Thrombopoietin, polypeptide cytokine composed of 332 amino acids, activates the production of platelets by stimulating the differentiation and proliferation of megakaryocytes through the receptor and is expected as a medicine for hemopathy accompanied with the unusual number of platelets, for example, thrombocytopenia and the like. DNA sequences encoding the thrombopoietin receptor have been described in Non-Patent 1. Low molecular peptides having an affinity for the thrombopoietin receptor is also known in Patent 1 and Patent 2, but these peptide derivatives are not generally practical for oral administration.
As a low molecule compound having an affinity to the thrombopoietin receptor, 1,4-benzodiazepine derivatives are described in Patent 3 and Patent 4,1-azonaphthalene derivatives are described in Patent 5, N-(4-phenyl-1,3-thiazol-2-yl)carboxamide derivatives are described in Patent 6, Patent 7, Patent 8, Patent 9, and Patent 10.                Patent 1: JP98/72492        Patent 2: WO96/40750        Patent 3: JP99/1477        Patent 4: JP99/152276        Patent 5: WO00/35446        Patent 6: WO01/07423        Patent 7: WO01/53267        Patent 8: WO02/059099        Patent 9: WO02/059100        Patent 10: JP98/287634        Non-Patent 1: Proc. Natl. Acad. Sci., 89, 5640-5644 (1992)        